Research On Design Criteria Forinverted Filter Based On Pore Characteristics

The damage survey result of the dam around the world shows that dam damage caused by infiltration accounts for more than 40% of all accidents.Therefore,it is of great importance to the safety of the dam.The use of the filter layer can not only keep the impermeable body stable,but also fully ensure the drainage effect of the drainage body,which significantly improve the safety of the earth and rock-fill dam.Thus,it is important to study the filter layer.The existing theory of filter layer design mainly focus on the study of the particle size.In fact,for the protected soil,soil particles study is the key to the infiltration damage and for the filter layer,however the pore study.The particle characteristics study of the soils of the protected soil and the pore characteristics study of the filter layer can be combined and compared to reflect the characteristics of the filter.In this paper,a series of seepage test,laser particle size analysis test,mercury intrusion test,and the simulation of discrete element software were carried out.The conclusions are as follows:?1?The smaller the effective pore diameter of the protected soil and the greater the dry density of the protected soil,the greater the critical slope of the protected soil.The impervious strength of the protected loess as the dependent variable,the effective pore diameter of the filter layer and the dry density as the independent variable,the least squares method for multiple regression analysis is utilized to acquire the weight of the two main factors,which provides reliable data support for the importance of filter layer.?2?In the existing design of the filter layer,the safety factor can be greatly optimized.Under the premise of complying with the requirement of standard drainage,the proposed method can be used to predict critical hydraulic gradient,which can effectively reduce the value of safety factor,and save money.?3?The particle size of easily eroded soil mainly varies within the particle size of d 50 of the protected soil,and with the decrease of the particle diameter of the filter layer,the concentration of the eroded particles increases.?4?Laser method and the hydrometer have a good correlation.And it is feasible to use the laser particle size analyzer to measure particles instead of the traditional hydrometer.In addition,the laser method has the advantages of wide measurement range of particle size,good reproducibility,fast measurement and simple operation,which provides a great convenience for the measurement of soil loss in the anti-seepage test.Now the laser particle size analyzer isn't widely used to get the soil particle gradation curve.?5?The mercury intrusion test is mainly used to measure the pore distribution characteristics of the interior of the block or of the surface of the powder.The method is not mature enough to measure the pore distribution of the granules.?6?The two-dimensional filter layer consistent with the requirements of the design specification?SL274-2001?,was simulated by discrete element software,and the pore size distribution curve of the filter layer was obtained by CAD.The pore diameter on the curve is compared with the effective pore diameter obtained by the interpolation method,and an effective pore diameter D_p20 is got.?7?The filter design criteria based on pore characteristics for viscous soils with particles less than 0.075 mm accounting for more than 85% was obtained under the premise of existing specifications.The criterion is the supplement of the existing norms and truly reflects the nature of the anti-filtration protection and the relationship between the filter layer pores and the protected soil particles.It can be used in the piratical project.